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Features of Nuclear Reactions with Light Weakly Bond Nuclei at Energy near the Coulomb Barrier
Skobelev, N. K.; Penionzhkevich, Y. E.; Kroha, Václav; Burjan, Václav; Hons, Zdeněk; Mrázek, Jaromír; Piskoř, Štěpán; Šimečková, Eva; Voskoboynik, E. I.
2012 - English
In the experiments carried out by ion beam He-6 of the cyclotron complex DRIBs (JINR) and He-3 beam cyclotron U-120M of the NPI, Czech Academy of Sciences have been investigated reaction Sc-45+He-3, He-6 and Au-197+He-3, He-6 in the energy range near the Coulomb barrier. It were obtained the experimental values of the cross sections for complete fusion reactions and direct reactions for formation of the isotopes Sc-43, Sc-44 and Sc-46 also Au-196 and Au-198 as a function of the bombarding He-3 and He-6 energy. Despite the low binding energy of He-3 and the positive Q-values leading to the formation of isotopes Sc-44 and Sc-46 also Au-196 and Au-198, the behavior of the excitation functions with the formation of these isotopes is different from the excitation functions for d, He-6.
Keywords:
He-6; cyclotron U-120M; cross section
Available at various institutes of the ASCR
Features of Nuclear Reactions with Light Weakly Bond Nuclei at Energy near the Coulomb Barrier
In the experiments carried out by ion beam He-6 of the cyclotron complex DRIBs (JINR) and He-3 beam cyclotron U-120M of the NPI, Czech Academy of Sciences have been investigated reaction Sc-45+He-3, ...
Experimental Determination of Neutron Room Background at the NPI Cyclotron U-120M
Štefánik, M.; Bém, Pavel; Honusek, Milan; Katovsky, K.; Majerle, Mitja; Novák, Jan; Šimečková, Eva
2012 - English
During the operation of external neutron generators of the Nuclear Physics Institute of The Academy of Sciences of the Czech Republic, the neutron room background is produced in cyclotron hall. To assess this effect, the neutron room background was measured using the activation method of dosimetry foils. To unfold the background spectrum from the set of measured reaction rates, the method of spectrum description by the special analytical function was employed.
Keywords:
activation detector; external neutron generator; gamma-ray spectroscopy; isochronous Cyclotron U-120M; neutron room background; neutron spectrum reconstruction; reaction rate; white neutron spectrum
Available at various institutes of the ASCR
Experimental Determination of Neutron Room Background at the NPI Cyclotron U-120M
During the operation of external neutron generators of the Nuclear Physics Institute of The Academy of Sciences of the Czech Republic, the neutron room background is produced in cyclotron hall. To ...
Využití výpočtu aktivit 14CO2 pro rekonstrukci změn obsahu radiouhlíku v atmosféře
Světlík, Ivo; Fejgl, M.; Turek, Karel; Pachnerová Brabcová, Kateřina; Tomášková, Lenka
2012 - Czech
Cenné údaje pro upřesnění parametrů transportu uhlíku v přírodě poskytuje atmosférický 14CO2. Radioaktivní 14C umožňuje lépe vyčíslit některé údaje spojené s dobou zdržení uhlíku v jeho přirozených zásobnících nebo s rychlostí toku uhlíku mezi jednotlivými přírodními složkami jako jsou ovzduší, oceány a biota. Obsahem práce je odhad změn obsahu 14CO2 v atmosféře s využitím radiouhlíkové kalibrační křivky IntCal09 a údajů o koncentracích CO2 v ovzduší v průběhu posledních 50 tisíc let. Atmospheric 14CO2 provides valuable information for better specification of carbon transport in nature. Radioactive 14C allows calculating some data related to the residence time of carbon in natural sinks as the atmosphere, oceans and biota. The work presents the estimation of 14CO2 content temporal changes in the atmosphere using the radiocarbon calibration curve IntCal09 and data about CO2 concentration during last 50 thousands years.
Keywords:
Radiocarbon; 14CO2; volume activity; atmosphere; temporal changes
Available at various institutes of the ASCR
Využití výpočtu aktivit 14CO2 pro rekonstrukci změn obsahu radiouhlíku v atmosféře
Cenné údaje pro upřesnění parametrů transportu uhlíku v přírodě poskytuje atmosférický 14CO2. Radioaktivní 14C umožňuje lépe vyčíslit některé údaje spojené s dobou zdržení uhlíku v jeho přirozených ...
Nondestructive Neutron Diffraction Residual Stress Measurements in a Large Depth in Steels
Woo, W.; Em, V.; Mikula, Pavol; Šaroun, Jan; Seong, B. S.
2012 - English
Residual stresses can be effectively and nondestructively measured through a large thickness of e.g. welded plates, by means of a new design of a reactor-based neutron diffractometer. Most of the engineering neutron diffractometers have a difficulty in increasing neutron penetration capability over 25 mm total thickness in steels. However, it can be significantly enhanced up to 70 mm with 4-mm spatial resolution along the depth by using the wavelength selection in combination with neutron focusing by cylindrically bent perfect monochromator. Present paper presents details of neutron diffractometer performance and some results.
Keywords:
stress; analysis; neutron diffraction
Available at various institutes of the ASCR
Nondestructive Neutron Diffraction Residual Stress Measurements in a Large Depth in Steels
Residual stresses can be effectively and nondestructively measured through a large thickness of e.g. welded plates, by means of a new design of a reactor-based neutron diffractometer. Most of the ...
Nedestruktivní stanovení dusíku v biologických a jiných materiálech fotonovou aktivační analýzou
Krausová, Ivana; Mizera, Jiří; Chvátil, David; Krist, Pavel; Řanda, Zdeněk; Kučera, Jan; Štursa, Jan
2012 - Czech
Je uveden postup stanovení dusíku v biologických materiálech instrumentální fotonovou aktivační analýzou (IPAA). Stanovení je založeno na měření nespecifického anihilačního záření gama o energii 511 keV radionuklidu 13N, produktu fotojaderné reakce 14N(γ, n)13N, který je čistým pozitronickým zářičem. Bylo testováno stanovení dusíku v koncentracích pod 1 % v biologických referenčních materiálech - NIST RM 8433 Corn Bran, 1547 Peach Leaves, 8414 Bovine Muscle a 1577b Bovine Liver. Optimalizovaný postup byl použit pro stanovení dusíku v přáškových nanodiamantech pro lékařské účely. The study presents a procedure for assaying nitrogen in biologocial materials by means of instrumental photon activation analysis (IPAA). The determination has been based on counting of the non-specific 511 keV annihilation gamma rays of 13N, product of the photonuclear reaction 14N(γ, n)13N, which is a pure positron emitter. IPAA allowed determination of nitrogen down to 1 wt.%. in selected biological reference materials - NIST RM 8433 Corn Bran, 1547 Peach Leaves, 8414 Bovine Muscle, and 1577b Bovine Liver. The optimized procedure was applied also to assaying nitrogen in pulverized nanodiamond intended for medical purposes.
Keywords:
Instrumental photon activation analysis; nitrogen; biological materials; nanodiamonds
Available at various institutes of the ASCR
Nedestruktivní stanovení dusíku v biologických a jiných materiálech fotonovou aktivační analýzou
Je uveden postup stanovení dusíku v biologických materiálech instrumentální fotonovou aktivační analýzou (IPAA). Stanovení je založeno na měření nespecifického anihilačního záření gama o energii 511 ...
A new set-up for total reaction cross section measuring
Sobolev, Yuri, G.; Ivanov, M. P.; Kugler, Andrej; Penionzhkevich, Y. E.
2012 - English
The experimental method and set-up based on 4 P n-gamma-technique for direct and model-independent measuring of the total reaction cross section sigma(R) have been presented. The excitation function sigma(R)(E) for He-6+Au-197 reaction at the Coulomb barrier energy region has been measured. The measured data are compared with the summarized cross section which has been prepared by summing of measured cross sections of main reaction channels: 1n-transfer and Au-197(He-6, xn)Tl203-xn with x = 2 divided by 7 evaporation reaction channels.\n\n
Keywords:
cross section; reaction; measurement
Available at various institutes of the ASCR
A new set-up for total reaction cross section measuring
The experimental method and set-up based on 4 P n-gamma-technique for direct and model-independent measuring of the total reaction cross section sigma(R) have been presented. The excitation function ...
Urban Structure Analysis
Vašata, D.; Exner, Pavel; Šeba, Petr
2011 - English
The built-up land represents an important type of overall landscape. We analyse the structure of built-up land in largest cities in the Czech Republic and selected cities in the USA using the framework of statistical physics. To do this, both the variance of the built-up area and the number variance of built-up landed plots in circles are calculated. In both cases the variance as a function of a circle radius follows a power law. The obtained value of the exponents are comparable to exponents typical for critical systems. The study is based on cadastral data in the Czech Republic and building footprints GIS data in the USA.
Keywords:
Urban structure; critical systems; self-organized criticality
Available at various institutes of the ASCR
Urban Structure Analysis
The built-up land represents an important type of overall landscape. We analyse the structure of built-up land in largest cities in the Czech Republic and selected cities in the USA using the ...
Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Pizzone, R. G.; Lamia, L.; Bertulani, C. A.; Mukhamedzhanov, A.; Spitaleri, C.; Blokhinstev, L.; Burjan, Václav; Cherubini, S.; Hons, Zdeněk; Kiss, G. G.; Kroha, Václav; La Cognata, M.; Li, C.; Mrázek, Jaromír; Piskoř, Štěpán; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A.
2011 - English
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even sometimes impossible. In such cases the use of indirect methods can give a substantial help. The Trojan Horse Method (THM) is based on the quasi-free break-up of a nucleus, which can be described in terms of a cluster structure. In such applications the independence of THM results with different break-up schemes, was tested using the quasi free(3)He(Li-6,alpha alpha)H and He-3(Li-7,alpha alpha)H-2 reactions. Results were then compared with the direct behaviours obtained from available data as well as with the cross sections extracted from previous indirect investigations of the same binary reactions using a different nuclide as a Trojan Horse nucleus.
Keywords:
fusion reactions; indirect methods; cross section
Available at various institutes of the ASCR
Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even ...
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A.; Banu, A.; Cherubini, S.; Coc, A.; Crucilla, V.; Goldberg, V.; Gulino, M.; Irgaziev, B.; Kiss, G. G.; Lamia, L.; Mrázek, Jaromír; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tabacaru, G.; Trache, L.; Tribble, R. E.; Trzaska, W.; Tumino, A.
2011 - English
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy O-18(p, alpha) N-15 reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2(+) resonance. Since Gamma similar to 100 - 300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T similar to 0.510(9) K based over our new improved determination of its resonance parameters.
Keywords:
nuclear reactions; nycleosynthesis; abundances
Available at various institutes of the ASCR
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy ...
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
Exner, Pavel
2011 - English
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
Keywords:
quantum graphs; vertex coupling; tube networks
Available at various institutes of the ASCR
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
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